The present disclosure relates to battery systems having multiple sets of battery cells such that these sets are independently controlled during operation of the battery systems. More specifically, each set may be independently discharged and/or charged and have a different state of charge than any other set in the same battery system.
Battery systems are becoming more prevalent in a variety of electronic applications, from consumer electronics to electric vehicles. However, many challenges still remain to be addressed before these battery systems will compete or overtake conventional energy and power sources. For a long time, car batteries were primarily used to start vehicle internal combustion engines and/or supply electricity to various electronics of the vehicles, but were not used to power the drivetrain. With the advent of new battery technologies, more vehicles now utilize battery systems as a traction power source, such as traction batteries or secondary batteries for electrical vehicles. Most secondary (i.e., rechargeable) batteries useful as traction power sources, particularly high energy density batteries, do not function well at low temperatures and/or become unsafe or quickly degrade at high temperatures. Furthermore, different types of batteries may have different performance characteristics. For example, some batteries may have high energy density but low power output. Other batteries have high power output but low energy density. Power output characteristics may also vary differently with the state of charge for different types of batteries. Finally, different types of batteries have different operating temperature requirements.
When a particular type of battery cells is used for a particular application, it is often very difficult to address various different and often competing requirements, which results in many design compromises. For example, in a vehicle application, increasing the power output of a battery cell, which is needed to accelerate the vehicle, generally causes reduction in the cells' energy density, which reduces the range of the vehicle. At the same time, when different battery types are integrated into the same battery system, these challenges are further complicated by system requirements for exchanging energy (e.g., heat, electricity) between the different battery types, in ways that are efficient and commercially cost-effective.
Conventional battery systems and thermal management systems thereof have been inadequate to address the aforementioned challenges. Furthermore, conventional battery systems generally use a single type of battery for a given application. For example, an electrical car is typically powered by a single type of lithium ion battery, e.g., lithium cobalt oxide batteries, lithium iron phosphate batteries, and the like. As such, much work is still needed in the field to which the instant disclosure pertains to improve performance of battery systems, to more efficiently utilize new battery materials, and to integrate more than one type of battery into a given application.